Glycine max (L.) Merr. – seed – SRM 3234*

A temporary water mount was prepared by mixing the dry powder with water and waiting until the material was fully hydrated. The water mount was treated with iodine potassium iodide (IKI) to visualize starch grains.

SRM 3234 is a very fine powder of a light beige color. Under magnification, most debris consists of subcellular fragments of clear thin-walled cells, with few visualizable features. Occasional multicellular fragments mostly have a rather round appearance under low magnification. Cells in these fragments range from rounded-polygonal (10–30 µm in diameter) to rectangular (9–30 µm by 21–36 µm) or prism-shaped (12–24 µm by 60–100 µm); multiple cell shapes may be seen in close proximity. Some cells have slightly thickened walls (<3 µm), which survive in subcellular debris as linear or branched fragments and can also be seen attached to the remains of single cells. Rare flattened multicellular fragments, often angular in shape, with very thick cell walls represent pieces of the seed coat and hilar area. The cells of the seed coat are irregularly polygonal or elliptical, mostly 12–25 µm long, and closely packed together. Fragments of the outer layer of the seed coat appear to have convoluted surface ornamentation; essentially the whole volume of the irregularly elliptical to rounded-oblong cells is occupied by extremely thick cell walls, which have occasional pits (thin spots) giving them a rounded-segmented appearance. Treatment with iodine potassium iodide (IKI) can make starch grains visible. These are plentiful, usually borne in small clusters of about 4 (to 5) grains, occasionally in smaller deformed clusters or solitary. Individual grains are rounded and usually <2 µm in diameter; the clusters are normally subspherical and 4–6 µm in diameter. They have usually been released from cells by the fine powdering of the material, but rarely may be seen in intact cells, with multiple clusters present in each cell.

*National Institute of Standards and Technology Standard Reference Material 3234.